1. Field of the Invention
The present invention relates to an apparatus for detecting a remaining quantity of toner in an electrophotographic copying machine.
2. Description of the Prior Art
In general, in the case of a dry type electrophotographic copying machine in which a developer of a two-component system consisting of carrier particles and toner particles is used, the toner contained in the developer is progressively consumed in accordance with the copying operation. In view of this fact, an automatic toner supplementing device is provided so as to maintain the toner density or concentration in a predetermined range. However, in case the toner contained within a hopper of the toner supplementing device is completely exhausted, the supplementary toner supply or addition to the developer can not be effected, whereby the toner concentration in the developer is reduced, resulting in correspondingly degraded image quality of the replica. In order to prevent such undesirable phenomenon from occurring, it is necessary to provide a detection and alarm system for detecting when the quantity of toner remaining in the supply hopper is decreased below a predetermined level and then signalling to the attendant the necessity of supplementing the toner to the hopper.
However, most of the hitherto known electrophotographic copying machines are lacking in the provision of such detection and alarm system. As a consequence, the operator or attendant is liable for periodical inspection and supplementary supply of the toner, which is however actually often neglected.